JP4313708B2 - Ceramic carrier - Google Patents

Description

  The present invention relates to a ceramic carrier used as a carrier for carrying a catalyst in, for example, an exhaust gas purification catalyst for an automobile engine.

Conventionally, cordierite (2MgO · 2Al ₂ O ₃ · 5SiO ₂ ) having a low thermal expansion and high thermal shock resistance has been widely used as a ceramic carrier for a catalyst carrier. Conventional ceramic carriers generally have cordierite formed into a honeycomb shape, and the surface thereof is coated (coated) with γ-alumina, and then a noble metal catalyst is supported on the pores of γ-alumina to form a catalyst body. . The coating layer is formed because the specific surface area of cordierite is small and it is difficult to support a necessary amount of the catalyst component as it is.

  As described above, the conventional ceramic carrier is premised on the coating of γ-alumina having a high specific surface area. However, coating the surface of the carrier with γ-alumina, on the other hand, has a problem that leads to an increase in heat capacity due to an increase in weight. In particular, in recent years, it has been studied to reduce the heat capacity by thinning the cell walls of the honeycomb carrier for early activation of the catalyst, and the formation of the coating layer halves the effect. In addition, the thermal expansion coefficient is increased by the coat layer, and the pressure loss is increased by reducing the cell opening area.

  For this reason, various studies have been made on ceramic carriers capable of supporting a catalyst component without forming a coating layer. For example, the specific surface area of cordierite itself can be improved by a method of heat treatment after acid treatment, but this method has a problem that the crystal lattice of cordierite is destroyed by acid treatment or the like and the strength is lowered. Yes, not practical.

On the other hand, a ceramic carrier capable of directly supporting a catalyst component by replacing at least one of the elements constituting the base ceramic with an element other than the constituent elements has been proposed (Patent Document 1). . The ceramic carrier can directly support the catalyst component by chemical bonding, and a coating layer for improving the specific surface area is not necessary. In addition, since there is no problem of strength reduction due to acid treatment or the like, it is promising for automobile catalysts that require durability.
JP 2002-346383 A

  In the ceramic carrier of Patent Document 1, an element having a d or f orbital in its electron orbit can be used as an element substituted for a constituent element of the base ceramic. An element having d or f orbital is considered to be easily chemically bonded due to the donation of electrons because the energy level is close to that of the catalyst component.

  However, as a result of further studies by the present inventors, it has been found that the catalyst performance after thermal endurance varies greatly depending on the type and combination of substitution elements. In addition, the introduction of a substitution element may increase the thermal expansion coefficient, and it is a major issue to realize early activation while maintaining the characteristics of cordierite.

  The present invention has been made in view of the above circumstances, and its purpose is to specify the optimum substitution element type and combination, substitution amount, etc., in a ceramic carrier that directly supports a catalyst component by element substitution, An object of the present invention is to obtain a high-performance ceramic carrier that realizes early activation of a catalyst by direct loading while maintaining the excellent characteristics of ceramic, and that is not easily thermally deteriorated.

In order to solve the above-mentioned problems, the ceramic carrier according to claim 1 uses cordierite as a base ceramic, and replaces at least one of its constituent elements with W and Ti as second component elements other than the constituent elements. By doing so, at least one or more kinds of noble metal elements among Pt, Rh, Pd, Ru, Au, Ag, Ir, and In can be directly supported as a catalyst component . Furthermore, the substitution ratio of W with respect to the constituent element is greater than 5%, and the ratio of the substitution amount of W with respect to the constituent element and the substitution amount of Ti is in the range of W: Ti = 1: 5 to 1: 8 By setting the cordierite crystal ratio in which Ti is dissolved to 25 mol% or more, a high-performance directly supported ceramic carrier is realized.

W as the second component element is bonded to the supported catalyst component with a strong force. However, the amount of solid solution in cordierite is small with W alone, and a sufficient improvement in catalyst characteristics cannot be expected. Therefore, in the present invention, the combination of W and other elements was examined, and the combination of W and Ti was found to be most effective. Ti introduced as a second component element together with W has an action of promoting solid solution of W in cordierite. It also promotes the formation of cordierite crystals.
The solid solution ratio and cordierite crystal ratio of W can be adjusted by the substitution amounts and ratios of W and Ti. In order to increase the solid solution amount of W, the ratio of the substitution amount of Ti to the substitution amount of W is preferably set to 5 times or more, and the solid solution ratio tends to increase as the ratio increases. However, when W reaches the solid solution limit, the solid solution rate does not increase any more, and usually desired catalyst characteristics can be obtained by setting the Ti substitution amount in the range of 1 to 8 times the W substitution amount.
Here, if the ratio of cordierite crystals in which W and Ti are dissolved in the entire substrate is 25 mol% or more, a sufficient amount of catalyst component can be directly supported by chemical bonding, and thermal degradation is suppressed. High effect. Therefore, it is possible to achieve early activation of the catalyst by direct loading and high thermal durability while maintaining the excellent characteristics of cordierite.

  In the ceramic carrier of claim 2, the cordierite crystal ratio in which W and Ti are dissolved is 30 mol% or more.

  Preferably, the substitution amount and ratio of W and Ti can be adjusted so that the ratio of cordierite crystals in which W and Ti are dissolved in the whole substrate can be 30 mol% or more. At this time, more catalyst components can be directly supported by chemical bonding, and the effect of suppressing thermal deterioration is improved. Further, an increase in the amount of cordierite crystal with low thermal expansion increases the effect of suppressing an increase in the thermal expansion coefficient, greatly improving the catalyst characteristics.

In the ceramic carrier of claim 3, the solid solution ratio of W in the cordierite crystal is 1.0 atm% or more.

Preferably, if the solid solution ratio of W in the cordierite crystal is 1.0 atm% or more, more catalyst components can be directly supported by chemical bonding, and thermal deterioration is suppressed, The particle size of the catalyst can be maintained at 10 nm or less, and the catalyst characteristics can be improved. The solid solution rate of W can be adjusted by changing the substitution amount and ratio of W and Ti.

In the ceramic support of claim 4, the solid solution ratio of W in the cordierite crystal is in the range of 1.5 to 8.0 atm%.

More preferably, if the solid solution ratio of W in the cordierite crystal is 1.5 atm% or more, more catalyst components can be directly supported by chemical bonding, and thermal deterioration is suppressed. The catalyst characteristics can be greatly improved. Further, if the solid solution ratio of W is 8.0 atm% or less, a stable cordierite crystal structure can be obtained, so that a low thermal expansion catalyst carrier can be realized.

Ceramic support according to claim 5, to 90% or less substitution rate of Ti and W for the constituent elements in total.

  In the ceramic support of claim 6, the solid solution rate of Ti in the cordierite crystal is 1 to 3 times the solid solution rate of W.

  When the ratio of the substitution amount of W and Ti is in the range of claim 5 above, the solid solution rate of Ti in the cordierite crystal is usually 1 to 3 times the solid solution rate of W. Good catalytic properties can be obtained.

  Hereinafter, the present invention will be described in detail. The ceramic carrier of the present invention can directly support a catalyst component such as a noble metal catalyst by substituting at least one of its constituent elements with a second component element other than the constituent element using cordierite as the base ceramic. This is a directly supported ceramic carrier. In the ceramic carrier of the present invention, W and Ti are used as the second component element, and the cordierite crystal ratio in which W and Ti are dissolved is 25 mol% or more, preferably 30 mol% or more. The shape of the ceramic carrier is not particularly limited, and may be various shapes depending on the application such as a honeycomb shape, a foam shape, a hollow fiber shape, a fiber shape, a powder shape, or a pellet shape. Applications include a carrier for an exhaust gas purification catalyst for automobiles and the like.

Cordierite, the base ceramic, has a theoretical composition of 2MgO · 2Al ₂ O ₃ · 5SiO ₂ , low thermal expansion, and excellent thermal shock resistance, so it can be used for exhaust gas purification catalysts that require high-temperature durability. Suitable as a carrier. However, it is difficult to support the catalyst component on the cordierite surface by physical adsorption or the like, and in the present invention, the catalyst component is bonded to the second component element introduced into the cordierite composition.

As the second component element, a combination of W and Ti is optimal. The second component element has a stronger bonding force with a catalyst component such as a noble metal catalyst than the constituent elements (Mg, Al, Si) of cordierite that is a base ceramic, and can be chemically bonded to the catalyst component. An element, specifically, an element having an empty orbit in its electron orbit and having two or more oxidation states is suitable. Here, the electron arrangement of W is [Xe] 4f ¹⁴ 5d ⁴ 6s ² , and the electron arrangement of Ti is [Ar] 3d ² 4s ² , both of which have an empty orbit in the d orbit. The oxidation number of W is II, IV, V, VI, etc., and the oxidation number of Ti is II, III, IV, etc., and has two or more oxidation numbers.

  An element having an empty orbit in the d orbital is close in energy level to the supported catalytic metal element and is likely to exchange electrons. Also, an element having two or more oxidation numbers is likely to transfer electrons to and from the catalyst. Among them, W is close in energy level to the noble metal element, and can be bonded to the catalyst with a strong force without a coating layer by such bonding by transfer of electrons. However, with W alone, the amount of solid solution in cordierite is small, and sufficient improvement in catalyst characteristics cannot be expected. Therefore, in the present invention, the introduction of a plurality of elements was examined, and a combination of W and Ti with the best performance was found. In this combination, W is mainly bonded to the noble metal catalyst, and Ti has an action of promoting solid solution of W in cordierite.

  When the second component element is W and Ti, good catalyst characteristics can be obtained by setting the cordierite crystal ratio in which W and Ti are dissolved to 25 mol% or more, preferably 30 mol% or more. If the cordierite crystallinity is less than 25 mol%, the number of binding sites for supporting the catalyst component by chemical bonding is reduced, and the effect of suppressing thermal degradation is lowered, so that the catalytic properties after thermal durability deteriorate. In addition, since the proportion of crystals other than cordierite increases, the characteristics as a carrier deteriorate, for example, the coefficient of thermal expansion increases. Here, the cordierite crystal ratio in which W and Ti are in solid solution indicates the ratio of cordierite crystal in which W and Ti are in solid solution in the entire base material of the ceramic carrier.

  In this case, if the solid solution rate of W in the cordierite crystal is usually in the range of 0.1 to 8.0 atm%, a necessary amount of the catalyst component can be supported. If the solid solution ratio of W in the cordierite crystal is smaller than 0.1 atm%, the number of binding sites for supporting the catalyst component by chemical bonding is reduced, and thermal degradation tends to occur. Catalytic properties deteriorate. Preferably, when the solid solution ratio of W is 0.5 atm% or more, and more preferably 1.0 atm% or more, the binding sites for supporting the catalyst component by chemical bonding increase. As a result, aggregation of the catalyst component is suppressed and high dispersion can be achieved with a particle size of 10 nm or less, thereby improving the effect of suppressing thermal degradation. If the solid solution ratio of W in the cordierite crystal is larger than 8.0 atm%, a stable cordierite crystal structure in which W and Ti are dissolved cannot be formed. It becomes unsuitable as a carrier.

  Therefore, normally, W and Ti are dissolved so that necessary catalyst loading can be secured without lowering mechanical properties such as strength and thermal expansion coefficient, heat resistance, and weather resistance of the base ceramic. The optimum catalyst characteristics are obtained by adjusting the cordierite crystal ratio and the solid solution ratio of W in the cordierite crystal. In order to adjust the cordierite crystal ratio, the selection of the starting material is important, and it varies depending on the substitution amount and ratio of W and Ti. In order to adjust the solid solution ratio of W, the substitution amount and ratio of W and Ti are important. Since cordierite can maintain a crystal form in a wide composition range, the cordierite crystal ratio and the solid solution ratio of W can be adjusted by changing the composition within the range.

  The ceramic carrier of the present invention is manufactured as follows. That is, a raw material in which the raw materials of the constituent elements (Mg, Al, Si) to be substituted with the second component element are reduced in advance according to the substitution amount from the raw material having cordierite having a theoretical composition. A compound serving as a raw material for the binary elements (W, Ti) is added according to the substitution amount. The ceramic raw material is kneaded, shaped, dried by a usual method, and then fired in the air atmosphere. Alternatively, from a raw material in which cordierite has a theoretical composition, a raw material obtained by reducing the raw materials of constituent elements (Mg, Al, Si) to be substituted with the second component element in advance according to the substitution amount is used. After being kneaded, shaped and dried, it is immersed in a solution containing the compound of the second component element (W, Ti). This may be dried and then fired in an air atmosphere.

  As the cordierite raw material, specifically, clay minerals such as talc are suitably used as the Mg source, and alumina and aluminum hydroxide are suitably used as the Al source. As the Si source, kaolin is generally used, but preferably an amorphous silicon oxide such as fused silica is used. When amorphous silicon oxide is used as a starting material, the effect of suppressing the formation of crystals other than the target cordierite and increasing the cordierite crystal ratio can be obtained. Moreover, there exists an effect which reduces a thermal expansion coefficient.

In order to increase the solid solution rate of W, which is the second component element, in the cordierite, the substitution amount of Ti is preferably in the range of 5 to 8 times the W substitution amount. In general, when the substitution amount of Ti is increased, the solid solution ratio of W tends to increase, but the saturation is obtained at a certain substitution amount or more. Therefore, it is preferable that the Ti substitution amount be at least 5 times the W substitution amount and less than 7 times. At this time, the solid solution rate of Ti in the cordierite crystal is usually 1 to 3 times the solid solution rate of W, and good catalyst characteristics can be obtained in this range. The solid solution ratio and cordierite crystal ratio of W vary depending on the substitution amount and ratio of Ti and W. Therefore, the solid solution ratio and the W solid solution ratio are set so that optimum catalyst characteristics can be obtained by appropriately setting these. The cordierite crystallinity should be adjusted.

Here, TiO ₂ , MgWO ₄ , WO _{3 and the} like are generated as constituent components (different phase components) other than cordierite crystals. These are oxides such as W that could not enter the cordierite crystal lattice, Al, Mg, Si, etc. that were formed in the formation of the cordierite crystal lattice. , Ti and W remain in the matrix composed of cordierite in which the solid solution is formed. By performing X-ray diffraction measurement on the ceramic support, it can be verified that cordierite (matrix) in which Ti and W are dissolved and a heterogeneous phase not containing cordierite exist.

The ceramic carrier of the present invention thus obtained is bonded to the catalyst component with a strong force, hardly deteriorates by heat, has a low thermal expansion coefficient (usually 2.0 × 10 ⁻⁶ / ° C. or less), and has a high performance. A direct carrier. As the catalyst component to be supported on the ceramic carrier, for example, a noble metal element such as Pt, Rh, Pd, Ru, Au, Ag, Ir, In or the like is preferably used, and at least one kind selected from these noble metal elements or more Is used. Various cocatalysts can be added as necessary. Examples of the promoter include Hf, Ti, Cu, Ni, Fe, Co, W, Mn, Cr, V, Se, Rb, Sr, Y, Zr, Nb, Mo, Tc, Ru, Sc, Ba, Ka. And metal elements such as lanthanoid elements (La, Ce, Pr, Nd, Pm, Sm, Eu, Gd, Tb, Dy, Ho, Er, Tm, Yb, Lu) and oxides or composite oxides thereof One or more of these elements are used depending on the purpose depending on purposes such as deterioration suppression, oxygen storage capacity, and catalyst deterioration detection.

  In order to support these catalyst components on the ceramic carrier of the present invention, a method is generally used in which the ceramic carrier is immersed in a solution containing the desired catalyst component, dried and then fired. When two or more types of catalyst components are used in combination, a solution containing a plurality of catalyst components may be prepared and the ceramic carrier may be immersed. For example, when Pt and Rh are used as main catalyst components, a solution containing hexachloroplatinic acid and rhodium chloride can be used. Various cocatalyst components can also be used in combination. In general, the supported amount of the catalyst component is preferably in the range of 0.05 to 10 g / L for the catalyst noble metal and 1 to 250 g / L for the promoter.

(Examples 1 to 4 and Comparative Examples 1 to 12 )
In order to confirm the effect of the present invention, a ceramic carrier of the present invention was produced by replacing the constituents of cordierite with W and Ti as the second component elements by the following method. First, talc, fused silica, alumina, and aluminum hydroxide are used as the cordierite forming raw material, 10% of the Si source is W (first substitution element), and 50% of the Si source is Ti (second substitution). The starting material powders were prepared so as to be near the theoretical composition point of cordierite. An appropriate amount of a binder, lubricant, moisturizer, etc. is added to this blended raw material and kneaded by a conventional method, and formed into a honeycomb shape with a cell wall of 100 μm, a cell density of 400 cpsi (number of cells per square inch), and a diameter of 50 mm did. The obtained honeycomb formed body was dried and fired at 1260 ° C. in an air atmosphere to obtain a directly supported ceramic carrier of the present invention (Example 1).

  In order to support the catalyst noble metal as the main catalyst component on the directly supported ceramic carrier obtained as described above, 5 minutes in an aqueous solution in which 0.035 mol / L of chloroplatinic acid and 0.025 mol / L of rhodium chloride were dissolved. After dipping and removing the excess solution, it was dried and baked at 600 ° C. in an air atmosphere to be metallized. The catalyst loading was Pt / Rh = 1.0 / 0.2 g / L.

The purification performance and thermal expansion coefficient of the obtained ceramic catalyst body were measured, and the results are shown in Table 1. As for purification performance, the evaluation conditions were as follows, and the 50% purification temperature (new contact T50) of propylene (C ₃ H ₆ ) at this time was measured. The 50% purification temperature (T50) is a temperature at which the purification rate of propylene is 50% (see FIG. 1B). Further, the 50% purification temperature (inferior touch T50) after the thermal endurance test at 800 ° C. for 5 hours was measured, and the difference was shown as (inferior touch T50−new touch T50).
Ceramic carrier: 35cc (φ30 × L50)
SV: 41000 / hr
Gas composition: A / F = 14.55

  For comparison, ceramic carriers using Co, Zr, and Ga as the second substitution elements in substitution amounts shown in Table 1 were manufactured (Comparative Examples 1 to 3). Furthermore, W, Ti, and Zr were used as the first substitution element in the substitution amounts shown in Table 1, and ceramic carriers not using the second substitution element were produced (Comparative Examples 4 to 6). Catalysts were supported on these ceramic carriers by the same method to obtain ceramic catalyst bodies, and their purification performance and thermal expansion coefficient were measured. The results are also shown in Table 1.

As is apparent from Table 1, when no second substitution element is used, Comparative Example 6 using W as the first substitution element has the best purification performance and a low thermal expansion coefficient. However, when the second substitution element is combined with this, the purification performance is rather lowered or the thermal expansion coefficient is increased depending on the type of the second substitution element (Comparative Examples 1 to 3). On the other hand, in Example 1 in which W and Ti were combined, the 50% purification temperature before and after the thermal endurance test did not change, and the thermal expansion coefficient was 1.0 × 10 ⁻⁶ / ° C., resulting in thermal degradation. It is difficult to obtain a ceramic support with low thermal expansion.

Next, when the second component element is W and Ti, the difference between the substitution amount and the ratio of W and Ti and the effect due to the starting material of the Si source were examined. Ceramic carriers were produced in the same manner as in Example 1 above, with the substitution amounts and ratios of W and Ti changed as shown in Table 2 ( Comparative Examples 7 to 9). In addition, a ceramic carrier was manufactured in the same manner with respect to the Si source starting material using kaolin instead of fused silica and the substitution amount and ratio of W and Ti changed as shown in Table 2 (Example 2, Comparative Examples 10 and 11 ).
Furthermore, for comparison, a ceramic carrier was produced in which the second component element was only W and the starting material for the Si source was kaolin (Comparative Example 12 ).

The cordierite crystal ratio in which W and Ti were dissolved and the solid solution ratio of W in cordierite of the directly supported ceramic support obtained as described above were measured. The results are shown in Table 2. . The cordierite crystal ratio was measured by an X-ray diffraction method. At this time, first, a calibration curve is created by preparing a sample in which cordierite as a main component and TiO ₂ as a heterophasic component are mixed at an arbitrary ratio, and measuring the peak intensity of each component. Next, the samples of Examples 1 to 4 and Comparative Examples 7 to 12 are measured under the same conditions, and the cordierite crystal ratio is obtained from the prepared calibration curve. Measurement conditions were as follows.
Measurement conditions: Tube voltage 50 KV Tube current 200 mA Room temperature The solid solution rate of W was measured by TEM-EDX. First, the samples of Examples 1 to 4 and Comparative Examples 7 to 12 are pulverized and observed with a TEM (transmission electron microscope). This was quantitatively analyzed by EDX, and the obtained W concentration was defined as the W solid solution rate.

As is apparent from Table 2, in Comparative Example 7 in which the second component element is only W, even if the substitution amount is 30%, the cordierite crystal ratio is as low as 20 mol%, and the W solid solution ratio is also 0.2 atm%. Only. On the other hand, in Examples 1 to 4 in which W and Ti are combined, the cordierite crystal ratio is 25 mol% or more, and the W solid solution ratio is as high as 1.0 atm%. Furthermore, when the starting material of the Si source is fused silica, the cordierite crystal ratio increases, and the cordierite crystal ratio is as high as 30 mol% or more when the substitution ratio ( Ti / W ) is in the range of 1 to 8. Indicates. Compared with the case where the starting material of the Si source is kaolin with the same substitution amount and ratio , for example, when the ratio of substitution amount of W and Ti ( Ti / W ) is 1 to 5, Example 2, Comparative Example 10, while 11 cordierite crystal ratio is 25～30Mol%, example 1, the cordierite crystal index of Comparative example 7, 9 and 53～55Mol%, has almost doubled.

Further, from Examples 1 and 2 and Comparative Examples 7 to 11 , the larger the amount of substitution of W and Ti and the larger the ratio of the amount of substitution of W and Ti ( Ti / W ), the more solid the W in cordierite. There is a tendency for the dissolution rate to increase. For example, in Comparative Example 8 in which the substitution amounts of W and Ti are each 5%, the W solid solution rate is 0.5 atm%, while in Comparative Example 7 in which the substitution amounts of W and Ti are 10%, In Example 1 in which the solubility is 0.8 atm% and the substitution amounts of W and Ti are 10% and 50%, respectively, the W solid solubility is greatly improved to 1.5 atm%. However, in Examples 3 and 4 in which the ratio of substitution amount ( Ti / W ) exceeds 5, no increase in the W solid solution rate was observed, and it is considered that W reached the solid solution limit. In Examples 3 and 4 , the cordierite crystal ratio is lower than that in Example 1. Therefore, it is preferable that the substitution amount ratio ( Ti / W ) be smaller than 7.

Thus, the cordierite crystal ratio can be increased or decreased by changing the substitution amount and ratio ( Ti / W ) of W and Ti , the starting material, and the like. FIG. 1 (a) shows the results of producing various ceramic supports in this way and measuring the purification performance after the thermal endurance test. As the cordierite crystal ratio increases, 50% after thermal degradation is shown. The purification temperature (T50) is low. FIG. 1A shows that when the cordierite crystal ratio is 25 mol% or more, the 50% purification temperature (T50) after thermal degradation is about 400 ° C., and it has practically sufficient performance. When the cordierite crystal ratio is 30 mol% or more, the 50% purification temperature (T50) after thermal degradation is about 380 ° C. or lower, which is more effective in suppressing thermal degradation. FIG. 2 shows the result of measuring the purification performance after the thermal durability test in the same manner by changing the W solid solution rate of the ceramic support. If the W solid solution rate is 0.5 atm% or more, It can be seen that the 50% purification temperature (T50) after deterioration is about 400 ° C., and it has practically sufficient performance. If the solid solution rate of W is 1.0 atm% or more, the 50% purification temperature (T50) after thermal degradation is about 380 ° C. or less, which is more preferable.

FIGS. 3A and 3B show examples of cordierite crystal structures in which W and Ti are dissolved (when the W solid solution rate is 2.3 atm%). Also in each of the above examples, it was confirmed by the analysis by TEM-EDX that W and Ti were dissolved, and the solid solution ratio of W and Ti at this time was Ti / W = 1-3. It was. When the ratio of the substitution amounts of W and Ti is Ti / W = 5, the solid solution ratio is obtained, and it can be seen that Ti is more easily dissolved.

  FIG. 4 shows the result of examining the change in the catalyst particle size after the thermal endurance test by changing the W solid solution rate of the ceramic support in the same manner as described above. As shown in the figure, when the solid solution ratio of W is less than 0.5 atm%, the catalyst particle size is in the range of 10 to 25 nm or more, and it is easy to be thermally deteriorated because there are few binding sites. Presumed to be. On the other hand, when the solid solution rate of W is 0.5 atm% or more, the catalyst particle size after thermal deterioration can be made 10 nm or less. If the solid solution rate of W is 1.0 atm% or more, the catalyst particle diameter after heat deterioration can be made 5 nm or less, and it is more preferable.

  As described above, according to the ceramic carrier of the present invention, the amount of cordierite produced and the solid solution ratio of W can be selected by appropriately selecting the substitution amount and ratio of the second component elements W and Ti, the starting material, and the like. And a good catalyst carrier that does not deteriorate with a small amount of catalyst can be obtained.

(A) is a figure which shows the relationship between the cordierite crystal ratio and the 50% purification temperature after a thermal endurance test, (b) is a figure for demonstrating the measuring method of 50% purification temperature. It is a figure which shows the relationship between the solid-solution rate of W, and the 50% purification temperature after a thermal endurance test. It is a figure which shows an example of the cordierite crystal structure in which W and Ti dissolved. It is a figure which shows the relationship between the solid solution rate of W, and the catalyst particle size after a thermal endurance test.

Claims (6)

The base ceramic is cordierite, and at least one of the constituent elements is replaced with a second component element other than the constituent elements, so that at least one of Pt, Rh, Pd, Ru, Au, Ag, Ir, and In. A ceramic support capable of directly supporting one or more kinds of noble metal elements as a catalyst component, wherein the second component element is W and Ti, and the substitution rate of W with respect to the constituent elements is greater than 5%, The ratio of the amount of substitution of W and the amount of substitution of Ti with respect to the constituent elements is in the range of W: Ti = 1: 5 to 1: 8, and the cordierite crystal ratio in which W and Ti are dissolved is 25 mol% or more. A ceramic carrier characterized by being.   The ceramic carrier according to claim 1, wherein the cordierite crystal ratio in which W and Ti are dissolved is 30 mol% or more. The ceramic carrier according to claim 1 or 2, wherein the solid solution ratio of W in the cordierite crystal is 1.0 atm% or more. 3. The ceramic carrier according to claim 1, wherein the solid solution ratio of W in the cordierite crystal is in the range of 1.5 to 8.0 atm%. The ceramic carrier according to any one of claims 1 to 4, wherein a substitution ratio of Ti and W to the constituent elements is 90% or less in total .   The ceramic carrier according to any one of claims 1 to 5, wherein the solid solution ratio of Ti in the cordierite crystal is 1 to 3 times the solid solution ratio of W.